https://asr.urmia.ac.ir/ Applied Soil Research en daily 1 Fri, 22 May 2026 00:00:00 +0330 Fri, 22 May 2026 00:00:00 +0330 https://asr.urmia.ac.ir/article_121973.html Nitrogen is one of the most important nutritional elements required by rice plants, and its adequate supply will increase the final yield of the product. In recent years, the loss of chemical fertilizers in agriculture, including nitrogen fertilizers in rice fields, has reached its maximum. The periphyton biofilm formed on the surface of waterlogged paddy fields is known as the third phase between water and soil, primarily responsible for the cycle of nutrients in paddy fields. A research study was designed and conducted with 18 treatments in a completely randomized design to investigate the effects of natural and enriched periphyton with low-power and high-power denitrifiers as biological inhibitors, with or without rice husk biochar and grape seed powder as organic inhibitors, in controlling the process of nitrate regeneration in paddy fields. The research was carried out in the form of greenhouse cultivation of rice plants for 30 days. The results showed that the application of grape seed powder increased the total nitrogen and ammonium in the soil, as well as the total nitrogen, height and dry weight in the plant. The results related to the application of biochar indicated that this material was more successful than grape seed powder in increasing phosphorus and potassium in the soil and the accumulation of these two elements in plant tissue. On the other hand, the use of rice husk biochar decreased the ammonium amount and increased the nitrate amount in the soil, having a greater effect than grape seed powder in reducing nitrate reduction. According to the obtained results, the use of periphyton along with organic inhibitors in paddy fields can be used as a new solution to inhibit the nitrate reduction process and provide nutrients. https://asr.urmia.ac.ir/article_121977.html The accumulation and pollution of heavy metals in agricultural soils pose a serious global issue due to their toxicity, abundance of pollution sources, non-degradability, and persistence in the environment. The aim of this study is to assess the potential contamination of heavy metals in agricultural lands in Dhi Qar Province, southern Iraq, using pollution indices. In order to assess the pollution status of soils in the study area, 50 surface soil samples were collected from lettuce (Lactuca sativa) cultivated fields. The total concentrations of metals including copper (Cu), zinc (Zn), lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni) were measured in the soil samples. To quantify the risk of soil contamination by heavy metals, the geo-accumulation index (Igeo), contamination factor (CF), and ecological risk potential (Er) were also applied. The results showed that the average concentrations of Cu, Zn, Pb, Cd, Cr, and Ni in the soils were 1198, 2964, 332, 18, 171, and 11 mg kg-1, respectively. The levels of heavy metals—Cu, Zn, Pb, Cd, and Cr—exceeded acceptable limits in the study area. Based on the Contamination Factor (CF), Cd and Cr were classified as having high contamination levels (CF > 6), while Ni showed low contamination (CF ≤ 1). According to the Igeo index, Cd was in class six, indicating an extremely high contamination level, and it also had the highest ecological risk potential among the heavy metals studied. Analysis of the spatial distribution maps of the contamination factor indices showed that the highest concentrations of heavy metals occurred in the northern, central, southeastern, and parts of the southwestern regions. Therefore, regular monitoring of heavy metal concentrations and identification of pollution sources in the region’s soils are recommended to reduce and manage environmental and health risks. https://asr.urmia.ac.ir/article_121975.html Biochars, compared to other soil amendments, possess inherent properties such as high porosity, large specific surface area, abundant functional groups, and environmental safety, making them highly effective for remediating contaminated soils. This study aimed to investigate the kinetics of total petroleum hydrocarbons (TPH) degradation in contaminated soil under the influence of two types of biochar, namely wheat straw biochar (WSB) and spent mushroom substrate biochar (SMSB), applied at different rates.The experiment was conducted in a completely randomized factorial design with three factors: biochar type (two levels), biochar application rate (five levels: 0, 10, 20, 30, and 50 g kg⁻¹), and incubation time (six levels: 6, 12, 18, 24, 42, and 60 days), each in triplicate. Total petroleum hydrocarbons and microbial respiration were measured at defined intervals, and data were analyzed using R software (version 4.5).Two-way ANOVA results showed that biochar treatment, incubation time, and their interaction had significant effects on both TPH concentration and microbial respiration (p < 0.001). The degradation potential and reduction in TPH were evaluated using first-order and second-order kinetic models. For wheat straw biochar treatments, both models provided good fits with NRMSE < 5% and R² > 0.94, indicating reliable performance. In contrast, for SMS biochar, the models fitted well at lower application rates, whereas higher doses showed less accurate fitting, likely due to complex sorption–degradation interactions.Overall, the results demonstrated that biochars, particularly SMS biochar, significantly enhanced the biodegradation rate of TPH and reduced its half-life in contaminated soils. Therefore, biochar application can be considered an effective, sustainable, and eco-friendly strategy for improving soil quality and mitigating petroleum hydrocarbon pollution https://asr.urmia.ac.ir/article_121976.html A study was conducted to evaluate the effects of different zinc fertilizer sources on morphological, photosynthetic pigment, biochemical, and phytochemical traits of tomato (Lycopersicon esculentum) (cv. SAMAR). The experiment followed a completely randomized design with three replications under pot condition. The different fertilizer source treatments included zinc sulfate, zinc chelate (Zn-EDTA), and Nano-zinc (ZnO NPs) that each applied at three different concentrations (0, 2.5, and 5 mg/kg soil). All treatments and concentrations were added to potting soil. Different plant characteristics such as plant height, stem diameter, fruit weight, fruit yield per plant, chlorophyll a, and chlorophyll b content, beta-carotene, lycopene, vitamin C, total phenolic content, total flavonoid content, in fruit were measured. There was a significant difference between fertilizer sources. The maximum plant height (104.33 cm), the largest stem diameter (10.48 mm), and the largest fruit weight (133 g) were observed in the 5 mg nano-zinc concentration, and the minimum height (74 cm), stem diameter (11.8 mm), and the lowest fruit weight (69.66 g) were observed in the control treatment. All various zinc sources significantly improved the studied traits compared to the control. In all traits, nano zinc showed a greater effect in improving morphological indices, photosynthetic pigments, and biochemical parameters. https://asr.urmia.ac.ir/article_121978.html In crop production systems, increasing the availability of nitrogen in the soil is one of the most important factors affecting growth, development, and yield. Accordingly, a study was conducted to investigate the effect of applying different levels of zeolite and nitrogen on the yield, yield components, and the harvest index of wheat (Triticum aestivum L.). The experiment was conducted in a field-based split-plot design arranged in a randomized complete block design with three replications in the 2021–22 cropping season in the Dezful region, located in the north of Khuzestan province. The main plots in this experiment included the application of natural zeolite at four levels (0, 4, 8, and 12 ton.ha-1), and the subplots included the application of four levels of nitrogen (50, 100, 150, and 200 kg.ha-1) from a urea fertilizer source. Comparison of the average experimental data showed that the highest number of spikes per square meter (503.3), number of spikelet per spike (15.44), number of grains per spike (31.20), 1000-grain weight (40.27 g), grain yield (5061 kg.ha-1), and biological yield (14176.8 kg.ha-1) were obtained with the treatment combination of applying 12 tons of zeolite along with 200 kg of nitrogen per hectare. Unlike the other evaluated traits, as nitrogen levels increased from 50 to 200 kg.ha-1, the harvest index decreased, so that the maximum harvest index (44.34%) was obtained in the treatment with 50 kg of nitrogen and 12 tons of zeolite per hectare. Finally, according to the test results, the application of different levels of zeolite (especially the level of 12 ton.ha-1) along with nitrogen fertilizer can be recommended as an effective mechanism for increasing nitrogen availability, improving yield components, and enhancing wheat yield. https://asr.urmia.ac.ir/article_121979.html Drought is one of the most important environmental stresses that limits the growth and production of agricultural products worldwide. Nowadays, the use of biostimulants in agriculture to enhance plant growth and performance under abiotic stresses has attracted considerable attention. Accordingly, in order to investigate the effect of vegetal protein hydrolysates (VPHs) application (as foliar application at concentrations of 2 and 4 ml L-1, fertigation at concentrations of 1.5 and 3 ml L-1, and control without protein application) under drought stress conditions (40, 70 and 100% of field capacity) on some morphological, physiological and phytochemical characteristics of sage (Salvia officinalis), a pot experiment was conducted as a factorial experiment in completely randomized design with three replications. The results showed that drought stress reduced plant height, stem diameter, leaf number, leaf and stem fresh and dry weight, chlorophyll content, net photosynthesis rate, stomatal conductance, transpiration, leaf nitrogen, phosphorus and potassium content, essential oil content and yield. However, the use of VPHs, improved growth indices, photosynthetic pigments and parameters, enhanced the uptake of nitrogen, phosphorus and potassium, and increased essential oil content and yield. So that in the fertigation treatment with a concentration of 3 ml L-1, plant height, stem diameter, number of leaves, leaf dry weight, total chlorophyll content, net photosynthesis rate, leaf nitrogen content, essential oil content and yield increased by 52.29, 12.38, 28.94, 39.66, 21.78, 20.1, 72.48, 13.14 and 60.87 percent, respectively, compared to the treatment without protein application. The findings of this study showed that VPHs can be used as an effective biostimulant to improve growth and nutrition and increase essential oil production of medicinal plants under drought stress conditions. https://asr.urmia.ac.ir/article_121974.html Vegetables, as a key source of many valuable compounds, play an important role in ensuring food security and human nutrition. Recently, the use of compounds and elements as foliar sprays has improved the quality and growth of plants. Among them, gamma-aminobutyric acid (GABA) is a non-protein amino acid and zinc is an essential nutrient for plants and humans, which play an important role in plant metabolism. This research was carried out as a factorial and completely randomized design with two foliar spray treatments including Nano ZnO and GABA in three replications and their effects on the growth and phytochemical traits of leaves and fruits of hot pepper plant (C. annuum) were investigated. In this study, morphological and phytochemical traits (in leaf and fruit tissue) and some elements in leaf tissue were investigated. In all measured traits, the applied treatments showed significant differences compared to the control. The results of morphological traits showed that the highest fruit fresh weight (12.60 g) was obtained in the treatment of 1 mM GABA with a concentration of 0 ppm Nano ZnO, and the highest fruit dry weight (2.47 g) was obtained in the treatment of 2 mM GABA with a concentration of 0 ppm Nano ZnO. The highest phenol content in leaves and fruits was 51.30 (2 mM GABA treatment) and 21.67 mg Gallic acid/gr FW in the combined treatment of 2 mM GABA and 150 ppm Nano ZnO. The highest flavonoid content in leaves and fruits was 6.32 and 4.91 mg quercetin/ gr FW in the combined treatment of 2 mM GABA and 150 ppm Nano ZnO, respectively. The highest antioxidant activity by DPPH method was observed in leaves and fruits, 77.71 % and 46.55 %, respectively. The results showed that in most phytochemical traits, the application of 2 mM GABA along with 150 ppm Nano ZnO increased the synthesis of compounds.